This is an easy classroom activity. Each student will need a straw, 2 test tubes, and bromothymol blue. Each group of two students can share a stopwatch.
Ask students to predict if exercise will affect cellular respiration, and, if so, in what way?
CHECK OUT MY TIKTOK VIDEO DEMONSTRATION BELOW, AND THEN READ ON FOR MORE DETAILS!
A class with 15-30 students can display their data on a graph to analyze the trends. "Typical" data can be provided for smaller classes so that they can graph a larger quantity of data points. Examples of "typical" before and after exercise times are:
Before Exercise (5:04, 4:09, and 4:14); After Exercise (2:03, 2:01, and 1:56).
Students can transfer their data to a graph like the one below.
After the class has completed the activity, ask students how exercising affected the time it took for the bromothymol blue to change color. Was their prediction correct? Discuss the bodily process the produces CO2 (cellular respiration).
This quick lab is a great addition to a Cellular Energy Unit. An organized lab form for this activity can be found here.
Gertrude Katz has spent over 30 years teaching K-12 public school students all major subjects. She has taught biology and education at the college level. The majority of her career has been spent instructing biology at the secondary level.